Field
Certain exemplary embodiments of the present invention relate generally to communication systems, and more particularly, to a direct device-to-device (D2D) communication integrated into a cellular network, such as a long-term evolution (LTE) or long-term evolution advanced (LTE-A) cellular network specified by the 3rd Generation Partnership Project (3GPP).
Description of the Related Art
Various abbreviations that appear in the specification and/or in the drawing figures are defined as below:
ACK Acknowledgement
BSR Buffer Status Report
CQI Channel Quality Indicator
C-RNTI Cell-Radio Network Temporary Identifier
CS Cyclic Shift
D2D Device-to-Device
DL Downlink
DCI Downlink Control Information
eNB evolved Node B
HARQ Hybrid Automatic Repeat Request
LA Link Adaptation
LTE Long Term Evolution
MCS Modulation and Coding Scheme
NACK Negative Acknowledgement
RRM Radio Resource Management
RS Reference Signal
RSRP Reference Signal Received Power
Rx Receiver
SINR Signal to Interference Plus Noise Ratio
Tx Transmitter
UL Uplink
Wireless communication systems are under constant development and continuing efforts are made to increase the performance and efficiency within such systems. In view of this, a promising feature of future wireless communication systems comprises direct communication between UEs in close proximity of each other, e.g., within a distance of a few tens or hundred meters. In future hybrid networks, a UE may be in a direct D2D mode in addition to a cellular mode. The D2D mode enables a number of potential gains over the traditional cellular technique, for example, capacity gains, peak rate gains and latency gains.
Take 3GPP LTE as an example, the D2D communication is set forth as an underlay to LTE cellular network operation, wherein both the cellular communication and the D2D communication use the same communication resources. In the D2D mode, the UE may communicate directly with another UE, and in the cellular mode, it may communicate with the other UE via a centralized controller in a conventional manner. The centralized controller is such as a BS, a Node B, or an eNB. For a better understanding and easy discussion of the D2D communication, description will be made with reference to FIG. 1.
FIG. 1 illustrates an example of a communication system 100 in which certain embodiments of the present invention can be practiced. As illustrated in FIG. 1, the communication system 100 comprises two cells (Cell 1 and Cell 2) which respectively include BSs 101 and 106 and are depicted in circles. Although two cells are illustrated, as one of ordinary skill would readily appreciate, the system 100 can include any number of cells. Within the coverage areas of the BSs 101 and 106 are seen a plurality of UEs, including D2D and cellular types of UEs. In the coverage area of the BS 101, D2D UEs 104 and 105 are communicating with each other in a D2D mode and cellular UEs 102 and 103 are communicating with or via the BS 101 in a cellular mode. The similar also occurs within the coverage area of the BS 106.
As seen from FIG. 1, due to their close proximity, D2D UEs in the D2D communication might confront with different interference from different sources. For example, a pair of D2D UEs in the D2D communication may be subject to interference from other D2D UEs. Also, the pair of D2D UEs at issue may be subject to interference from cellular UEs that are in cellular communication via the BS. Take the D2D UEs 104 and 105 as examples, if they are assigned (or reuse) the same radio resource as the cellular UE 102 or 103, they may be subject to interference from the cellular UE 102 or 103. Further, if they are allocated the same radio resources as the D2D UE 108 or 109 or cellular UE 107 in the neighboring cell (i.e., Cell 2), they may experience interference from the neighboring cell. This may lead to a problem of how to properly allocate radio resources and efficiently perform LA in view of the above-mentioned interference, especially in such a hybrid network including a cellular network and a D2D network.